Venetian blind-type shutter



Marfih 1957 E. MULLER 3,307,472

VENETIAN BLIND-TYPE SHUTTER Filed April 6, 1964 v 2 Sheets-Shet 1 2 Sheets-Sheet 2 Filed April 6, 1964 FIG United States Patent 3,307,472 VENETIAN BLIND-TYPE SHUTTER Ernst Miiller, Schwenningen (Neckar), Germany Filed Apr. 6, 1964, Ser. No. 357,593 Claims priority application Germany, Apr. 10, 1963, H 48,810 3 Claims. (Cl. 98116) The invention relates to a shutter for a fan or blower and particularly to those equipped with a number of superimposed slats or louvres which normally hang vertically. These slats are pivotally mounted in the vicinity of their upper edges and can be swung into a substantially horizontal position either by hand or under the action of the air pressure or vacuum exerted by the fan or blower.

Plastics slats, compared with those of light metal such as aluminum, have the advantage that, even with very humid acidic air like that extracted from stables and even after a very long period of operation, they remain free from corrosion and do not form electrolytic cells with the metals of other components, such as the pivotal shafts.

In order to achieve the desired stability of conventional plastics slats, they must be thick and relatively heavy. In the case of automatically opening shutters, a large opening force is therefore required to swing the slats into the substantially horizontal position; otherwise the individual plastics slats will be swung only slightly and block the outlet of the fan, thus greatly reducing the ventilating effect.

The invention aims to provide an improved shutter for which the slats can be made rapidly and cheaply without a great deal of labour and material and, although being stable with a sufficiently strong closing force, can be swung into a substantially horizontal position with a very low opening force,

According to the invention, a Venetian blind-type shutter comprises slats each of which is pivoted about an axis in the vicinity of its top edge so as to hang in a substantially vertical plane under gravity or be swung out of the vertical under the influence of the air stream set in motionby the fan or blower, wherein each pivotal axis divides the associated slat into two imaginary portions of which the upper portion (as viewed in the hanging position) presents a smaller surface area to the air stream and is heavier than the lower portion.

The closing force is achieved in that the heavier portion above the pivotal axis tends to swing the lighter portion because of the difference in torque, i.e. the slat is in unstable equilibrium; Each slat lies on the surface of the underlying slat and the closing force is produced by the torque which acts on the lower surface of the slat to bring it into stable equilibrium. The difference between the surface areas is necessary to make opening possible when the fan is switched on. The heavier surface then swings against the direction of air flow.

With regard to the actual construction, there are a great many different possibilities. One is for the upper portion to be made of a material of higher specific weight, such as metal, in contrast to the lower portion which can be made of plastics material. a

This is a structurally simple way of obtaining a situation in which the center of gravity is displaced within the slat so as to produce a closing force, i.e. so that the slat is stable only when it hangs substantially vertically. As already mentioned, the surface areas of the slats must be of different sizes above and below the pivotal axes, so that the dynamic pressure produced by these surfaces allows the slats to be opened, since the surfaces and thus the dynamic pressures are different and the torque which now arises acts against the closing force.

In a preferred embodiment, the slats are of plastics ma- Patented Mar. 7, 1967 terial and metal rails which also carry a pivotal shaft, are attached to the upper portion.

The meta-l rails may be joined to the plastics by riveting or impressing or they may be inserts in an injection moulding process, and the slat may be in sheet or foil form.

It is also possible for the portions above the pivotal axis to be in supporting form. In this construction the plastics slats are of uniform thickness and their top edges have a widened portion similar to the profile of the supporting fins. An extrusion process is used for this embodiment. Care must be taken that no great variations in section obtain along the extruded profiles, in order to prevent the profile from warping. Metal bars are subsequently placed in the pocket formed in this way.

Instead of using an extrusion process to make the slat, it can be made of a material of uniform thickness which is folded back on itself along the upper edge to form an elongated flat pocket. In this embodiment, the material is again concentrated above the center of gravity when the slat hangs vertically. The weight of this conwntrated material, in conjunction with the arrangement of the pivotal shaft beyond the center of gravity, produces a closing moment in the opposite direction to the airstream, and this ensures that the individual plastics slats bear on one another with a suflicient closing force. However, as soon as the airstream causes the slat to swing slightly outwardly, the weight of the material above the center of gravity gives rise to a torque directed against the closing moment, so that only slight opening force is required to swing the individual slats into a substantially horizontal position.

In a preferred embodiment of the invention, the slats are made of material of uniform thickness which is folded back along the top edge to form an elongated flat pocket which widens the profile.

If the slats are designed in this way, no special and expensive pressing tools are required to make them. Plas tics material in plate form is warmed along one edge, folded back and welded to form the elongated fiat pocket. This also greatly increases the lengthwise stability of the slats.

In order to concentrate the material above the pivotal axis in spite of the plastics material being thin and folded into a pocket, the invention provides for metal inserts to be arranged in the material of the plastics sheet between the top edge and the pivotal axis so as to displace the center of gravity towards the top edge.

The use of metal inserts enables the center of gravity of the slat to be displaced far enough in the direction of the top edge to bring it just under the pivotal axis, so that very slight pressure is sufiicient to swing the slat substantially horizontally.

In a preferred embodiment of the invention, the metal inserts are in the form of fiat bars and are arranged inside the pocket. If the metal inserts are arranged and designed in this way, cheap commercial strip material can be used and can be inserted in the pocket in the simplest manner.

In a modified embodiment of the invention, the metal inserts are in the form of round rods which are readily commercially obtainable and cheap. The advantage of using rod inserts is that the plastics material need not be folded sharply back along the top edge. The resultant flat pocket has a drop-shaped profile, which is known to have favourable aerodynamic characteristics.

Another advantage of the slat according to the invention is that the pivotal shaft can be arranged in the pocket adjacent the metal insert but closer tothe center of gravity of the profile. As a result of this feature, the pivotal shaft may advantageously also be in the form of a commercially obtainable metal bar. Thus, the slat according to the invention can be produced by using very little labour on assembly. 1

An example of the invention is illustrated in the accompanying drawings, wherein:

FIG. 1 is a part-sectional fragmentary view of a sh-utter as seen in the direction of air flow,

FIG. 2 is a section taken along the line II-II in FIG. 1,

FIG. 3 is a part-sectional fragmentary view of a modified embodiment,

FIG. 4 is a section taken along the line IVIV in FIG. 3,

FIGS. 5 and 6 are fragmentary sections of one of the slats of FIG. 2 but on a much larger scale, and showing the location of the center of gravity in two positions of the slat,

FIG. 7 is a cross-section through a flat slat, and

FIG. 8 is a side elevation of FIG. 7.

FIGS. 1 and 2 show superimposed plastics slats 1 which normally hang vertically and which are each equipped with a pivotal shaft 2 arranged in the vicinity of the top edge 3 of the slat. The shaft 2 extends beyond both sides of the slat and these extensions are mounted in bearings 4 forming part of the shutter. The slats 1 are made of plastics material of uniform thickness which is folded back along the top edge 3 so as to form an elongated narrow pocket 5 along the whole length of the slat. The pivotal shaft 2 is pushed through this elongated narrow pocket 5. In order that the center of gravity of the slat 1, 5 can be displaced towards the top edge 3, a metal insert in the form of an elongated flat bar 6 is inserted in the pocket 5 above the shaft 2; the bar 6 also secures the shaft 2 inside the pocket.

It will be seen particularly clearly from FIGS. 5 and 6 that, when the plastics slat 1 is hanging in its normal vertical position, the pivotal shaft 2 is parallel to the top edge 3 with its center line located between the top edge 3 and the center of gravity 7 but displaced from the latter in the opposite direction to the airstream 8. As the result of this construction, the gravity force component in the direction of the arrow 9 is spaced a relatively large distance 111 from the center line of the shaft 2 when the slat hangs vertically. The resulting closing moment which urges the slat in the direction of the arrow 11 is just large enough to make the slat bear closely against the subjacent slat and to enable the opening in the fan to be closed with suflicient pressure. However, as soon as an air current in the direction of the arrow 8 acts on the slat 1, it moves into the FIG. 6 position. It will be seen from this figure that the gravity component in the direction of the arrow 9 is now spaced only a short distance 12 from the center line of the shaft 2. Thus the closing moment in the direction of the arrow 11 of FIG. 5 is reduced in the FIG. 6 position and the slat 1 can be brought into the substantially horizontal position under the action of the airstream in the direction of the arrow 8.

The arrangement of the pocket 5 at the top edge 3 of the slat 1 gives the latter considerable longitudinal stability. This is further increased by the insertion of the metal bar 6, so that very thin plastics material may be used for ma king the slat 1. In view of the low weight of very thin plastics slats it may happen that the metal bar 6 is too heavy if it is of the same length as the slat. In such a case the bar '6 may be shortened acwrding to requirements, as shown in FIG. 1,

In a modified embodiment which is illustrated in FIGS. 3 and 4, the material of the slat 1 is folded back with a slight curve at the top edge 3 instead of sharply. For an embodiment of this type it is an advantage to use metal inserts in the form of round bars 13; any gap left between the bar 13 and the shaft 2 can be filled in with a plastics bar 14. A plastics fin designed in this way has a substanitally drop-shaped or streamlined profile, which offers little resistance to the airstrea'm when the slat is swung out.

In FIGS. 7 and 8 a lighter, lower portion 15 of the slat is of plastics sheet. It is joined to the upper portion 16 above the shaft 2 by a projection 17 in a construction similar to a slot and feather connect-ion. The projection may be pressed or stuck into the slot in the sheet 15. The top edge 3 may be rounded in order to reduce the flow resistance when the slats are substantially horizontal upon airflow in the direction of the arrow 8.

The invention can be used in all cases, irrespective of what materials are used, wherein slats are opened or closed by air flow, the center of gravity being displaced by varying the specific weight above and below the pivotal axis, so that the difference is small enough to produce a closing force which can easily be overcome. If the same material were used, the difference would be great enough to make the closing force excessive, in which case there would be a considerable reduction in the efiiciency of the fan and in the amount of air supplied.

What we claim is:

1. A ventilator shutter including fan means comprising slats of one-piece construction each of which is pivoted about an axis adjacent its top edge to define upper and lower portions, said slats adapted to hang in a substantially vertical plane under gravity and adapted to be also swung out of the vertical under the influence of an air stream set in motion by the fan means, and wherein each pivotal axis divides the associated slat into two portions of which the upper portion presents a smaller surface area to the air stream than the lower portion, means for pivoting the slats, the upper portion of each slat having a higher specific gravity than the lower portion, inserts mounted in the slats between their top edges and their pivotal axis, the upper section of each of said slats being bent to form pockets, andwherein the said inserts consist of bars positioned in said pockets provided in the slats.

2. The structure as defined in claim 1, wherein the bars have an elongated fiat construction.

3. The structure as defined in claim 1 wherein the bars have an elongated cylindrical formation.

References Cited by the Examiner UNITED STATES PATENTS 1,272,064 7/1918 Lezius 98-119 X 2,355,412 8/1944 Bird 98-119 3,204,548 9/1965 McCabe 98-119 I FOREIGN PATENTS 398,176 8/1933 Great Britain. 485,850 5/1938 Great Britain.

' ROBERT A. OLEARY, Primary Examiner. 

1. A VENTILATOR SHUTTER INCLUDING FAN MEANS COMPRISING SLATS OF ONE-PIECE CONSTRUCTION EACH OF WHICH IS PIVOTED ABOUT AN AXIS ADJACENT ITS TOP EDGE TO DEFINE UPPER AND LOWER PORTIONS, SAID SLATS ADAPTED TO HANG IN A SUBSTANTIALLY VERTICAL PLANE UNDER GRAVITY AND ADAPTED TO BE ALSO SWUNG OUT OF THE VERTICAL UNDER THE INFLUENCE OF AN AIR STREAM SET IN MOTION BY THE FAN MEANS, AND WHEREIN EACH PIVOTAL AXIS DIVIDES THE ASSOCIATED SLAT INTO TWO PORTIONS OF WHICH THE UPPER PORTIONS PRESENTS A SMALLER SURFACE AREA TO THE AIR STREAM THAN THE LOWER PORTION, MEANS FOR PIVOTING THE SLATS, THE UPPER PORTION OF EACH SLAT HAVING A HIGHER SPECIFIC GRAVITY THAN THE LOWER PORTION, INSERTS MOUNTED IN THE SLATS BETWEEN THEIR TOP EDGES AND THEIR PIVOTAL AXIS, THE UPPER SECTION OF EACH OF SAID SLATS BEING BENT TO FORM POCKETS, AND WHEREIN THE SAID INSERTS CONSIST OF BARS POSITIONED IN SAID POCKETS PROVIDED IN THE SLATS. 